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Formatted question description: https://leetcode.ca/all/1357.html

# 1357. Apply Discount Every n Orders (Medium)

There is a sale in a supermarket, there will be a discount every n customer.
There are some products in the supermarket where the id of the i-th product is products[i] and the price per unit of this product is prices[i].
The system will count the number of customers and when the n-th customer arrive he/she will have a discount on the bill. (i.e if the cost is x the new cost is x - (discount * x) / 100). Then the system will start counting customers again.
The customer orders a certain amount of each product where product[i] is the id of the i-th product the customer ordered and amount[i] is the number of units the customer ordered of that product.

Implement the Cashier class:

• Cashier(int n, int discount, int[] products, int[] prices) Initializes the object with n, the discount, the products and their prices.
• double getBill(int[] product, int[] amount) returns the value of the bill and apply the discount if needed. Answers within 10^-5 of the actual value will be accepted as correct.

Example 1:

Input
["Cashier","getBill","getBill","getBill","getBill","getBill","getBill","getBill"]
[[3,50,[1,2,3,4,5,6,7],[100,200,300,400,300,200,100]],[[1,2],[1,2]],[[3,7],[10,10]],[[1,2,3,4,5,6,7],[1,1,1,1,1,1,1]],[,],[[7,3],[10,10]],[[7,5,3,1,6,4,2],[10,10,10,9,9,9,7]],[[2,3,5],[5,3,2]]]
Output
[null,500.0,4000.0,800.0,4000.0,4000.0,7350.0,2500.0]
Explanation
Cashier cashier = new Cashier(3,50,[1,2,3,4,5,6,7],[100,200,300,400,300,200,100]);
cashier.getBill([1,2],[1,2]);                        // return 500.0, bill = 1 * 100 + 2 * 200 = 500.
cashier.getBill([3,7],[10,10]);                      // return 4000.0
cashier.getBill([1,2,3,4,5,6,7],[1,1,1,1,1,1,1]);    // return 800.0, The bill was 1600.0 but as this is the third customer, he has a discount of 50% which means his bill is only 1600 - 1600 * (50 / 100) = 800.
cashier.getBill(,);                           // return 4000.0
cashier.getBill([7,3],[10,10]);                      // return 4000.0
cashier.getBill([7,5,3,1,6,4,2],[10,10,10,9,9,9,7]); // return 7350.0, Bill was 14700.0 but as the system counted three more customers, he will have a 50% discount and the bill becomes 7350.0
cashier.getBill([2,3,5],[5,3,2]);                    // return 2500.0


Constraints:

• 1 <= n <= 10^4
• 0 <= discount <= 100
• 1 <= products.length <= 200
• 1 <= products[i] <= 200
• There are not repeated elements in the array products.
• prices.length == products.length
• 1 <= prices[i] <= 1000
• 1 <= product.length <= products.length
• product[i] exists in products.
• amount.length == product.length
• 1 <= amount[i] <= 1000
• At most 1000 calls will be made to getBill.
• Answers within 10^-5 of the actual value will be accepted as correct.

Related Topics:
Design

## Solution 1.

• class Cashier {
private int i;
private int n;
private int discount;
private Map<Integer, Integer> d = new HashMap<>();

public Cashier(int n, int discount, int[] products, int[] prices) {
this.n = n;
this.discount = discount;
for (int j = 0; j < products.length; ++j) {
d.put(products[j], prices[j]);
}
}

public double getBill(int[] product, int[] amount) {
int dis = (++i) % n == 0 ? discount : 0;
double ans = 0;
for (int j = 0; j < product.length; ++j) {
int p = product[j], a = amount[j];
int x = d.get(p) * a;
ans += x - (dis * x) / 100.0;
}
return ans;
}
}

/**
* Your Cashier object will be instantiated and called as such:
* Cashier obj = new Cashier(n, discount, products, prices);
* double param_1 = obj.getBill(product,amount);
*/

• class Cashier {
public:
Cashier(int n, int discount, vector<int>& products, vector<int>& prices) {
this->n = n;
this->discount = discount;
for (int j = 0; j < products.size(); ++j) {
d[products[j]] = prices[j];
}
}

double getBill(vector<int> product, vector<int> amount) {
int dis = (++i) % n == 0 ? discount : 0;
double ans = 0;
for (int j = 0; j < product.size(); ++j) {
int x = d[product[j]] * amount[j];
ans += x - (dis * x) / 100.0;
}
return ans;
}

private:
int i = 0;
int n;
int discount;
unordered_map<int, int> d;
};

/**
* Your Cashier object will be instantiated and called as such:
* Cashier* obj = new Cashier(n, discount, products, prices);
* double param_1 = obj->getBill(product,amount);
*/

• class Cashier:
def __init__(self, n: int, discount: int, products: List[int], prices: List[int]):
self.i = 0
self.n = n
self.discount = discount
self.d = {product: price for product, price in zip(products, prices)}

def getBill(self, product: List[int], amount: List[int]) -> float:
self.i += 1
discount = self.discount if self.i % self.n == 0 else 0
ans = 0
for p, a in zip(product, amount):
x = self.d[p] * a
ans += x - (discount * x) / 100
return ans

# Your Cashier object will be instantiated and called as such:
# obj = Cashier(n, discount, products, prices)
# param_1 = obj.getBill(product,amount)


• type Cashier struct {
i        int
n        int
discount int
d        map[int]int
}

func Constructor(n int, discount int, products []int, prices []int) Cashier {
d := map[int]int{}
for i, product := range products {
d[product] = prices[i]
}
return Cashier{0, n, discount, d}
}

func (this *Cashier) GetBill(product []int, amount []int) (ans float64) {
this.i++
dis := 0
if this.i%this.n == 0 {
dis = this.discount
}
for j, p := range product {
x := float64(this.d[p] * amount[j])
ans += x - (float64(dis)*x)/100.0
}
return
}

/**
* Your Cashier object will be instantiated and called as such:
* obj := Constructor(n, discount, products, prices);
* param_1 := obj.GetBill(product,amount);
*/